I myself have a few language-courses in my shelf: (German, Serbian, Turkish, Albanian, French, Chinese and English EFL) for different reasons. I lack Spanish though! Can anyone tell me about the major differences in Spanish spoken in Spain and Mexico/Latin America? Are they huge or simply dialects?
I am from Chile, born in Argentina, have Mexican, Salvadorian, Guatemalan, Peruvian Cuban, and White friends that speak Spanish. I have some friends which have been to Spain, as well.
The main difference in Spanish between these countries is the same as can be found in English. These are the regional pronunciations, phrases, and accents, which can be heard(and sometimes seen in written language) in the different "dialects" which exist today. For someone whose native language is English, it is quite easy to differentiate the accents and regional expressions between someone from England, the South(US), Boston, Midwest US, Canada, Australia, etc. In Spanish, it is basically the same.
However, I think there are more regionalisms in Spanish than in English, since every Spanish speaking country has developed its own "dialect" ever since el Castellano(Spanish) was introduced to the Americas and nations gained their independence from colonial rule in the early 1800's. This regionalism has been further accelerated by the use of mass media. For example, when I lived in Santiago, Chile, my friends and I would always yell "Que vacán!" to denote that something was "cool" or "awesome". Another example is that in Chile, people tend to say "Que penca" when they think something is lame. I still use the term "Que penca" to this day. I asked my Peruvian friend if he had ever heard of such a thing, and he told me that he had not(Peru is adjacent to Chile).
In Spain, some pronounce the "z" like "th" in the word "thump". I once heard an Argentinean man say "seguíme" instead of "sigueme"(although one example should not lead one to generalize an entire population, I have enough experience with Spanish to back up this claim). Chileans also say "choclo" to refer to corn, when other Spanish speakers would say "maíz" or "(forgot what else, but my Salvadorian friends have another name for this)". Also, we say, "pasto" for grass, while Mexicans usually call it "zacate(not sure how to spell this since I don't use the word)". I could go on for ages.
In conclusion, there are many regionalisms in Spanish. Too many even for fluent Spanish speakers to keep track of. Every day, Spanish,influenced by cultures in different countries is developing in a different manner. I would like to point out that "Mexico/Latin America" should be divided into so many more subgroups of different dialects. However, the differences in these regionalisms are not great enough to seriously impede communication between, let's say, a Mexican Spanish speaker and a Spanish Speaker from Spain, or any other place.